Suppressing the formation of SiC during the magnesiothermic reduction of SiO₂–C composite is still challenging. In this paper, the formation of SiC can be tentatively controlled by tuning the reactivity of reductants that can be modulated by alloying with Si at different atomic ratios. The reduction product is SiC when using Mg as the reductant, while the C–Si composites are formed when using the reductants with relatively low reactivity (e.g., Mg–Si alloy, Ca–Si alloy). The obtained C–Si composites reduced from C–SiO₂ show excellent electrochemical performance, delivering a specific discharge capacity of 925 mAh g⁻¹ at 1 A g⁻¹ after 200 cycles and 825 mAh g⁻¹ at 2 A g⁻¹ after 300 cycles. In addition, when bio-silica is used as Si resource, the C–Si composites prepared from the rice husks also exhibit excellent electrochemical performance, delivering a specific discharge capacity of 687 mAh g⁻¹ at 2 A g⁻¹ after 300 cycles. Overall, the revealed reactivity–composition relationship can be extended to selectively prepare carbon- or carbide-based target materials as well as to harvest both C and Si from Si-containing waste biomasses.

_{在 SiO 2} -C 复合材料的磁热还原过程中抑制 SiC 的形成仍然具有挑战性。在本文中，可以通过调整还原剂的反应性来初步控制 SiC 的形成，还原剂可以通过与不同原子比的 Si 合金化来调节。当使用镁作为还原剂时，还原产物是碳化硅，而当使用反应活性较低的还原剂（如镁-硅合金、钙-硅合金）时，会形成碳-硅复合材料。_{由 C-SiO 2}还原得到的 C-Si 复合材料表现出优异的电化学性能，在 200 次循环后在 1 A g ^{-1下提供 925 mAh g -1}的比放电容量，在 2 A g -1 下提供825 mAh g ^-1300 次循环后^{-1 。}此外，当使用生物二氧化硅作为Si资源时，由稻壳制备的C-Si复合材料也表现出优异的电化学性能，在2 A g ^-1循环300次后的比放电容量为687 mAh g ^{-1 。}总体而言，揭示的反应性-成分关系可以扩展到选择性地制备碳或碳化物基靶材料，以及从含硅废生物质中收获 C 和 Si。